For the purpose of preventing the oxygen oxidation of various articles that deteriorate or degrade easily under the influence of oxygen, typified by foods, drinks, medicines, cosmetics, and the like, and storing them for a long period, oxygen absorbents for removing oxygen in packages housing these are used.
As the oxygen absorbent, an oxygen absorbent comprising an iron powder as a reaction basis is generally used in terms of oxygen absorption ability, ease of handling, and safety. But, this iron-based oxygen absorbent responds to a metal detector, and therefore, it is difficult to use a metal detector for foreign matter inspection. In addition, a package enclosing the iron-based oxygen absorbent cannot be heated by a microwave oven because of the risk of ignition. Further, the oxidation reaction of the iron powder is utilized, and therefore, the oxygen absorption effect can be exhibited only for objects to be stored that are of a high moisture type.
In addition, a packaging container is developed in which the container is composed of a multilayer material in which an oxygen-absorbing layer comprising an oxygen-absorbing resin composition obtained by blending an iron-based oxygen absorbent with a thermoplastic resin is disposed, and thus, an improvement in the gas barrier properties of the container is promoted, and an oxygen absorption function is provided to the container itself (see Patent Literature 1). But, similarly, problems of the packaging container are such that it cannot be used for a metal detector, cannot be heated by a microwave oven, and exhibits the effect only for objects to be stored that are of a high moisture type. A further problem is such that the internal visibility is insufficient due to the problem of opacity.
From the circumstances as described above, an oxygen absorbent comprising an organic substance as a reaction basis is desired. As the oxygen absorbent comprising an organic substance as a reaction basis, an oxygen absorbent comprising ascorbic acid as a basis is known (see Patent Literature 2).
On the other hand, an oxygen-absorbing resin composition comprising a resin and a transition metal catalyst and having oxygen trapping properties is known. For example, a resin composition comprising a polyamide, particularly a xylylene group-containing polyamide, as an oxidizable organic component and a transition metal catalyst is known, and further, there are also illustrations of a resin composition having an oxygen trapping function, an oxygen absorbent obtained by molding the resin composition, a packaging material, and a multilayer laminated film for packaging (see Patent Literature 3).
In addition, as an oxygen-absorbing resin composition that does not require moisture for oxygen absorption, an oxygen-absorbing resin composition comprising a resin having a carbon-carbon unsaturated bond and a transition metal catalyst is known (see Patent Literature 4).
Further, as a composition for collecting oxygen, a composition comprising a polymer comprising a substituted cyclohexene functional group or a low molecular weight substance to which the cyclohexene ring is bonded and a transition metal is known (see Patent Literature 5).